Liquid depth gauge



June 21, 1960 J. STEENFELD ETAL 2,94l,403

LIQUID DEPTH GAUGE Filed April 29, 1955 a U r////////// INVENTORS JOSEPHSTEENFELD 4 GEORGE K Zro W A OR Y United States Parent O LIQUID DEPTHGAUGE Joseph Steenfeld, North Arlington, and 'George V. Zito,

Northvale, NJ., assignor to Bendix Aviation Corporation, Teterboro, NJ.,a corporation of New Jersey Filed Apr. 29, 1955, Ser. No. 504,836

7 Claims. (CI. 73-304) This invention relates to liquefied gasconverters, in which a supply of liquefied gas is maintained in acontainer, from which gas evaporated from the liquid is withdrawn asneeded. Systems of this kind are used to supply oxygen to high-flyingaviators.

Apparatus of this type must be provided with -arrangements forintroducing liquid to replenish the supply when required, and shouldinclude means for indicating the amount of liquid in the container. Thisis efiectively accomplished by an electrical system including aWheatstone bridge having in one arm a condenser immersed in the liquidand extending vertically throughout the liquid depthrange, an oscillatorcircuit for energizng the bridge and a bridge output circuit containinganindi cator actuated by variations in the capacity of the mmersedcondenser due to changes in liquid level. The indicator may be locatedat a point remote -from the container, which is provided with atransmitter unit including the immersed condenser, and preferably theother bridge elements and the oscillator circuit. The unit must beassociated with, and advantageously is removably mounted on, thecontainer, which is designed to provide insulation for the lowtemperature liquid, frequently being constructed with insulated innerand outer walls and a long neck to minimize the heat transfer byconduction.

An object of the invention is to provide a novel arrangement for inserting and supporting an immersion condenser in a container.

Another object is to provide an arrangement of this type that issuitable for use with a container having an elongated neck. I

A purpose is `to provide a novel arrangement for introducing liquid andwithdrawing gas from the container. A related purpose is to provide suchan arrangement in combination with an immersion condenser.

An object is to provide a unitary combination structure functioning bothas an immersion condenser and as liquid introduction and gas withdrawalmeans.

Another object is to provide a unitary fitting, removably mountable inthe container mouth and carrying as a unit an immersion condenser, aliquid supply and gas removal system, Components of an electricalcircuit responsive to liquid depth, or any combination of thesefeatures.

A particular object is to provide an improved immerson condenserConstruction, and especially one that is readily produced from standardmaterial and -s Conveniently and rapidly assembled, while maintaininghigh electrical eflicieney and responsiveness to liquid level changes.

A further purpose is to provide an mmersion condenser with simple andeificient radio frequency shielding suitable for efiicient operationwhen the condenser is energized -by a local oscillator circui-t. Arelated purpose is to provide such shielding in a simple, eflicient andrugged unitary construction.

Another object is to provide improved anangements for gas withdrawalfrom gas space above a submerged con denser unit.

The foregoing and other objects, purposes and advantages of the nventionwill appear more fully from consideraton of the detailed descriptionwhich follows, in conjuncton with the accompanying drawing wherein oneembodiment of the invention is illustrated. It is to be expresslyunderstood, however, that the drawing is for the purposes ofillustration and description, and is not to be construed as'defining thelimits of the invention.

In the drawing:

Fig. '1 is a somewhat diagrammatic vertical central section through anoxygen Converter system embodying the invention, with parts shown inperspective and broken away; and

Fig. 2 is an enlarged longitudinal central section through the lowerportion of the immersion condenser probe.

The invention is illust'ated in its application to an oxygen convertersystem which includes an insulated liquid oxygen' container or 'bottle10 having a body 11 and a neck 12,' both comprised of an inner Wall 13and an outer wall 14 with an insulating space 15, normally evacuated,between them. Walls 13 and 14 are sealed at the upper end of neck 12'toa metal cap -16 having a central mouth or'opening 17. Insulated bottlesof this type are known, and features thereof which Would normally beincluded in practice have been omitted from this showing for purposes ofSimplicity, since they have no relationship to the invention.

A fitting 18 of electrically conducting metal is mounted in the bottlemouth 17, as by threading neck 19 into said mouth so as to seal thebottle 10. An immersion condenser assem bly 20 'is mounted in neck 19and extends downwardly through the bottle neck 12 substantially tothebottom of the bottle 10, this type of assembly being generallyreferred to as a probe. It includes a condenser unit formed of platesinsulated from each other and extendng from substantially the bottom ofthe bottle 10 to a point above the maximum level 21.

The condenser unit forming part of assembly 20 may -advantageouslyterminate substantially `below the fitting neck 19, and of course abovethe maximum liquid level, as shownin the form illustrated. In this formthe condenser unit of probe 20, shown in detail in Fig. 2, includes aninner tubular condenser element 22, a-n intermediate tubular insulatedcondenser element 23 and an external tubular condenser element 24, allconcent rically arranged,

. and Conveniently cylindrical as in the illustrated embodiment.

The intermediate element 23 is supported and insulated by rings 25 ofinsulating material fitted around the inner eylinder 22 andbear ingagainst shoulders 26 on said cylinder Rings 25 are advantageouslyL-shaped in crosssection, andinclude a cylindrcal body portion 27fitting against the inner face of intermediate eylinder 23, and a radially extendingflange 28 fitting the inner surface of outer' eylinder24, and hearing against the adjacent end of the intermediate eylinder23. Abutting against the axially outerfaces of insulation ings 25 areannular metal retaining caps 29 fi-tting tightly around inner; eylinder22 and connected thereto as by soldering. Outer eylinder 24 fits snuglyaround caps 29 at its ends, and is suitably engagedtosaid caps, as byspinning the ends 30 of eylinder 24 around the adjacent margins of saidcaps'.

condenser 'assembly. 20 is provided with, openings through which liquidwill pass into the spaces 31, 32 jon either side ofintermediate eylinder23 and promptly as sume the same levelas the liquid outside of saidassembly.

with one 'or more openings 33; immediately ;adjacent` to= the bottomlevels of said spaces 31, 32, and intermediate height of the liquidcylinder 23 is likewise -provided with one or more openings 34 atsubstantially the same level. The arrangement is such that by properlypositioning and proportioning the lower cap 29 and adjacent insulationring 25, liquid at a very low level in bottle' will enter the condenserarrangement and register on the indicating system.

Similar openings 35 in inner cylinder 22 and openings 36 in intermediatecylinder 23 are provided immediately adjacent to the upper ends ofspaces 31, 32, and are located above the maximum height of liquid level21.

The assembly or probe 20' includes an arrangement for suspending thecondenser unit above described and for providing a connection betweenthe passage 37 within the inner cylinder 22. In the construction shown,the latter cylinder is extended through fitting neck 19 into fitting 18,and is attached thereto, as by soldering said cylinder 22 to an anrularsupporting fiange 38. The open upper end of passage 37 communicates witha liquid inlet passage 39 extending outwardly through a radial arm 40 ofsaid fitting, and advantageously threaded at its outer end to receive aliquid supply pipe 41.

The space 4-2 in bottle 10 above liquid level 21 is filled with gas,which in the case of an oxygen supply system consists of gaseous oxygenevaporated from the liquid in the lower part of the bottle. Anarrangement is pro vided for Withdrawing gas from space 42 as desired.For this purpose the fitting neck '19 is provided with an axial borelarger in diameter than the inner cylinder 22, which passes through andis spaced from the Walls of said bore to provide an annular passage 43communicating with a gas outlet passage 44 extending through radial arm45 of fitting 18, and advantageously threaded at its outer endto receivethe gas discharge pipe 46. The radial arms 40 and 45 may conveniently belocated opposite each other, With axially aligned outer openings, andpassages 39 and 44 are preferably arranged with passage 49 slopingupwardly to the inlet of passage 37, while passage 44 slopes downwardlyto a point below said inlet, flange 38 and the upper end of innercylinder 22.

It will be understood that the liquid oxygen supply arrangement and thegas discharge arrangement will normally be provided With numerousfeatures such as valves and Controls, which are not relevant to thisinvention and therefore have been omitted in the interests ofsimplicity.

The probe 20 is advantageously provided with gas withdrawal means.cylindrical casing 47 fitting within and attached to the outer wall ofthe outlet passage 43 in neck 19', as by soldering, and extendingdownwardly to the upper end of outer cylinder 24. Casing 47 and innercylinder 22 are spaced to form an annular gas passage 48 communicatingwith passages 43 and 44, and provided with suitable gas inlet means suchas openings 49 in said casing, advantageously near .the lower partthereof adjacent to the upper end of outer cylinder 24.

Casing 47 is preferably fixed to cylinder 24 to provide added supportand rigidity, being axially aligned with said cylinder in the llustratedembodiment, abutting the upper end of the latter cylinder and attachedthereto as 'by a cylindrcal connecting collaa' 50 fitting against theouter faces of casing 47 and cylinder 22 and firmly attached to saidcasing and cylinder as by soldering. As already indicated the condenserunit forming the lower portion of probe 20 is ,electrically connected toa crcuit responsive to variations in the capacity of said condensercaused by changes in the liquid level. A oircuit of this type is shown,for instance, in application Serial No. 498, 6 81, filed April l, 1955,by George V. Zito. Components of such a circuit, advantageouslyincluding all elements thereof except the indicator unit, are enclosedin a cas-ing 51 mounted on fitting 18 and forming a compact unitarystructure with the probe. As illustrated, said fitting is provided witha central positioning boss 52 to which the casing 51 is attached.

In the form shown this comprises a 2,941,4o3 i v An arrangement isprovided for connect-ing the condenser unit formed by cylinders 22, 23in said circuit. For this purpose electrically `connected cylinders 22and 24 may be on the ground side of the circuit and in communicationthrough fitting 18 with the ground side of the components in casing 51.An insulated lead 53 from said circuit is carried through aconnector 54set in an insulating plug 55 into passage 37, the lower end of lead 53passing through an opening 35 in the condenser portion of cylinder 22and being electrically connected at 56 to the insulated intermediatecylinder 23. Casing 51 may be ,provided with the usual plug socket 57,through which leads to the remote indicator and source of electricalenergy 'may be connected by 'a plug.

The probe 20 is arranged for convenient Construction, assembly andmounting on fitting 18, the probe being formed of metal cylinders ofstandard commercial type, With identical caps 29 and insulating rings25, which may be sld into place `on the inner cylinder 22 and fixed inposition engagng intermediate cylinder 23, after which the outercylinder 24 may be fixed in place. The casing 47 with collar 50 can thenbe positioned and attached to cylinder 24. Likewise the casing 47 andinner cylinder 22 are arranged for convenient mounting in and attachment to fitting 18. v

In operation, liquid oxygen is introduced through pipe 41 and passages39 and 37, fiowing out of the bottom of inner cylinder 22 into thebottle 10 and through open- *ings 33 and'34 'into the space 31 and 32,Where the liquid level will be maintained at the same height as that inthe bottle 10 and will suitably actuate the remote indicator. This makesit possible for the operator to regulate the supply of liquid oxygen byobserving the indicator. Gas may be withdrawn as desired through pipe46, passages 44, 43 and 48 and inlet openings 49, being replaced byevaporation from the liquid.

It will be evident that with this arrangement the entire liquid supplyand gas discharge system is carried by the fitting '18, which -alsocarries the condenser assembly or probe 20 and the electrical circuitelements in casing '51. This entire assembly may be inserted in orremoved 'from a -bottle 10 by simply screwing the neck 19 in or out ofthe bottle mouth 17.

It is also pointed out that the invention is eifective for'shielding thecondenser elements and leads carrying radio f-requency voltages. Theouter and inner tubular condenser elements 22 and 24 are conductivelyconnected to the fitting 18 and the frame of the circuit oasing '51which form one side of the circuit connected to :a reference voltage,usually ground; and the lead 53 from the insulated intermediate plate 23passes upward to the circuit elements in casing 51 through inner tubularelement 47 and fitting 18, providing continuous shielding.

,Although but one embodiment of the invention hasbeen illustrated anddescribed in detail, it is to be expressly understood that the inventionis not limited thereto. Various changes can be made in the design `andarrangement of the parts without departing from the spirit and scope ofthe invention, as the same Will now be understood by those skilled inthe art. For instance, the upper' part of the inner cylinder 22functions as 'a support for the condenser unit while the lower partoperates as an element of said unit; and while these parts are shown asintegral, this arrangement is not intended to be re- -strictiveLikewise, while the casing 47 in the form illustrated is fixed to thecondenser unit and acts as a support, 'being connected to the interierof the container 10 to openings 49, the invention is not limited to theuse of this casing nor its equivalent as a support, or 'to theparticular type of gas inlet illustrated.

We claim:

1. A liquid level sensing system for use with a liquid container having`a top opening, comprising a fitting `for said opening, a tubular metalsupport element mounted on said fittng and extending downwardly from thefittng, a coaxial tubular condenser unit carried by said support elementand having an open passageway communicating with the interier of saidtubular element, and a fluid passageway in the fittng communicating withthe interier of said tubular element, arranged for the passage of fluidthrough said fittng and support element.

2. A liquid level sensing system for use with a liquid container havinga top opening, comprising a fittng for said opening, -a tubular metalsupport element mounted on said fittng and extending downwardly from thefittng, a -tubular metal condenser element mounted concentrically on thelower part of and insulated from said support element, arranged forforming with the lower part of the support element and immersoncondenser unit, and a fluid passageway in the fittng communicating withthe interier of said tubular support element, arranged for the passageof fluid through said fittng and support element.

3. A liquid level sensing system for use With a liquid container having:a top opening, comprising a fittng for said opening, a tubular metalsupport element mounted on said fittng and extending downwardlytherefrom, a coaxial tubular metal condenser unit carried by saidsupport element and having an open passageway communicating with theinterier of said tubular element, and a fluid passageway in the fittngcommunicating with the interier of said tubular element, said fittngbeing provided with a second separate fluid passageway communicatingwith the upper part of the centainer.

4. A liquid level sensing system for use with a liquid container havinga top opening substantially above the liquid level in the container,comprising a fittng for said opening, an inner hollow metal cylindermounted on the fittng and extending downwardly therefrem, arranged toextend through said opening into the container below said liquid level,a liquid passageway through the fittng communicating with the interierof said cylinder, and an outer metal cylinder mounted on the fittngconcentric with and spaced from the inner cylinder below the fittng, andincluding an opening :for gas in the upper part contiguous to thefittng, said fittng including a gas passageway communicating with thespace between said cylinders.

5. A liquid level sensing system including a liquid centainer having atop opening, a fittng mounted in said opening, a liquid level sensingcondenser mounted on the fittng and extending downwardly into thecontainer, including a tubular condenser comprsing two concentric plateslocated in the container, a liquid supply passage in the fittng incommunication with the interier of said tubular condenser, and a gaspassage in s-aidvfitting in communication with the upper part of thecentainer.

6. A liquid level sensing 'system including a liquid container having atop opening, a fittng mounted in said opening and provided with apassage, a first tubular metal condenser plate mounted on the fittng incommunication with said passage and extending downwardly therefrom intothe container, a second associated tubular condenser plate concentrcwith said first plate, and means for mounting the second plate in`capacitve relation to and insulated from the first plate, said fittngincluding a second passage connected to an opening in the lower part ofthe fittng arranged to communicate with the upper part of the centainer.

7. A liquid level sensing probe for use with a liquid container having atop opening, comprising a fittng for said opening provided with apassage, a first 'tubular metal condenser plate mounted on the fittng:in communication with said pass-age and extending downwardly firom thefittng, a second -associated tubular metal condenser plate concentricwith said first plate and spaced from the fittng, and means forsupporting the second plate from the fittng, said fittng being providedwith a second passage having an opening in the lower face of the fittng,ar'anged for communication with the upper part of the centainer.

References Cited in the file of this patent UNITED STATES PATENTS2,127,875 Lippert Aug. 23, 1938 2,377,275 Smith May 29, 1945 2,563,280Shaefer Aug. 7, 1951 2,754,457 Meyer July 10, 1956 FOREIGN PATENTS455,731 Canada Apr. 5, 1949

